Collagen has been used as a pharmaceutical carrier, as a surgical prosthesis (sutures and wound dressings), and as an implant material. In many instances, the collagen is cross-linked with chemical agents, radiation, or other means to improve its mechanical properties, decrease its immunogenicity, and/or increase its resistance to resorption. For example, U.S. Pat. No. 4,424,208 describes a collagen composition including cross-linked collagen and reconstituted collagen fibers having enhanced persistence. While these materials are remarkably effective, they shrink in volume after implantation due primarily to absorption of their fluid component by the body, although the shrinkage (syneresis) is less than non-cross-linked collagen. Since a constant volume or persistence is desirable, an additional injection or injections of supplemental implant material is required. It would thus be advantageous to provide collagen compositions having enhanced persistence after being introduced in vivo to a soft tissue treatment site.